Rewiring a ballast. Help needed.

[Victor Roberts]

If you can find the ones with the electronic ballast (Shop Lights) they are
TINY.

The small ballasts used in shop lights are very poor quality. They are
usually a series C-L ballast that produces very high lamp current
crest factor which in turn results in short lamp life.

--
Vic Roberts
http://www.RobertsResearchInc.com
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[Don Klipstein]

The small ballasts used in shop lights are very poor quality. They are
usually a series C-L ballast that produces very high lamp current
crest factor which in turn results in short lamp life.

My bit of experience with a few of these is not only that mentioned
above, but also lower light output than with a good ballast.
A spikier lamp current give reduced efficiency because the low pressure
mercury arc is less efficient at higher instantaneous current. But in
addition to this, it appears to me that these cheap undersize "shop light"
ballasts do not even give full power to the lamp(s).

One more thing about those cheap "shop light" ballasts: At least some
of these are less tolerant of heat than good ballasts, and that is why
many cheap "shop lights" come with chains to hand them on - the ballast
may overheat if the fixture is mounted flush against a beam. (Not sure
the latter is good practice even with a good ballast, but I sure have the
impression that the cheap ballasts in cheap fixtures that mostly go into
basements, etc. tend to be fussier about heat and maybe anything else.)

What I like to do with cheap fixtures: Replace the ballast with an
electronic one for T8 lamps, trashpicked from a dumpster by a hospital
that has a new or recently renovated section being renovated (or renovated
again) - and check that the ballast takes 120V rather than 277V. Get T8
lamps.

- Don Klipstein (don@misty.com)

 

[JM]

quoting:

$1.40 - is this for 34w, 40W, or T8 tubes? The local GESupply sells 34w CW
tubes for about $1.30 currently, and about$2.50 for T8. 40W tubes are
currently about $2.25 .

8' for $6 to$7 - Is this for 60W or 75W tubes?

Replying to my own post here...

I just checked the price of the 8' tubes:

60w $2.71
75w $4.71


So figure that you'll need two 4' tubes to make an 8' section, if this were
around here, it would not be a large enough savings to make the switch. But,
just for the energy savings alone, it would still be worthwile to go to T8.

But, if you don't care about the energy savings, then I would just keep the
8' tubes, replace the dead ballasts, and relamp the dead tubes with 75w
ones for the the highest possible light output.






Rest of my OP still applies:

 

[NSM]

The small ballasts used in shop lights are very poor quality. They are
usually a series C-L ballast that produces very high lamp current
crest factor which in turn results in short lamp life.

Mine appear to use a triac as the ballast resistor.

N

 

[Victor Roberts]

Mine appear to use a triac as the ballast resistor.

A triac can't be a resistor. It has two only states: on and off. The
triac is probably used as a switch to start the lamp.

--
Vic Roberts
http://www.RobertsResearchInc.com
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[James Sweet]

One other question while on the topic of replacing ballasts and fluorescent
lights....
I am remodelling an empty unit to make a bookstore and they currently have
about fifteen to twenty 8 foot double tube lights throughout the store. (The
store is about 2500 square feet.)
I am considering replacing them all with about 50% more 4 foot units. (So
about 22 - 30 units.)
I am considering doing this mostly due to the high price of 8' tubes and
ballasts. (In this part of Canada the 4' tubes go for about $1.40, while the
8' go for about $6-$7). Also the ballasts for the 8' bulbs costs about $30,
whereas I can get a whole 4' unit for about that price. ($20 for a cheaper
one that will probably break down in a few years, $30 -$35 for one that
will hopefully last.)
So there are actually two questions:
1) Will I retain a similar amount of light from replacing those units? (I
know that their will be a small drop in light, but I just wanted to know how
noticeable it would be? Or should I just double the number of 8' units and
achieve near the same amount of light?)
2) Is it going to be cost effective over 10 -15 years to replace all these
units? (Or am I wasting a lot of money trying to avoid spending $6 -$7 on
the 8' tubes and $30 on a few new ballasts to replace the 3 or 4 that are
burnt out?)
Thanks for reading this long post, and for any answers or suggestions.
Sean.

If you're gonna bother to go through the effort and expense to replace all
those lamps, I strongly suggest you look into F32T8 trichromatic phosphor
lamps using electronic ballasts. The initial cost is higher, but they've
made the old T12 stuff obsolete. A 32W T8 trichromatic tube such as the
F32T8/830 or 850 is brighter than a 34W T12, and with the electronic ballast
you get no perceptible flicker. For a store, the greatly improved color
rendering of the trichromatic stuff (CRI >80 for the 800 series stuff) has a
lot of benefits, the reduced energy consumption and increased sales will pay
for the conversion. Additionally you have a wide choice of color
temperatures from 2700K (warm incandescent color) to 6500K (icy daylight)
with 3000K and 4100K being popular middle ground. Personally I like 5000K as
it's a nice pure clean white without being icey but it's a matter of
personal preference.

 

[NSM]

A triac can't be a resistor. It has two only states: on and off. The
triac is probably used as a switch to start the lamp.

Obviously they use some sort of driver circuit to control current to the
lamp via the triac. I would have assumed you knew that - from your own
website.

N

 

[James Sweet]

Thats the impression I get, but do the numbers. What does it cost you
to fix he few 8'ers and provide tubes, what does it cost for 4'...

I'd look at just replacing a small number with 4', just as needed, but
do it in one area to ensuer it looks decent, using the good 8' lamps in
that area to repair or replace the dead ones elsewhere.

Spot relamping is not a good idea in a retail business (or most places
really), discharge lamps suffer lumen depreciation as they age and should be
replaced on a time schedule. Otherwise they get dimmer and dimmer while
still consuming full power and if you spot relamp them you get bright spots
and dim spots and overall it just looks shabby. A better approach which is
more cost effective in the longrun is to run the lamps a specified number of
hours and then replace them all at once, though it's hard to get people over
the "incandescent mentality" of running any lamp completely into the ground.
As others have said, the cost of the electricity over the life dwarfs the
cost of the lamps and lost sales due to the store looking like a cave will
cost more than a set of new lamps. Look around and once you start noticing
this it'll drive you nuts, gets even more fun in places using metal halide
lighting as not only do the depreciate more substantially but they tend to
suffer color shift as they age. I've been in places with old mercury lights
that were so dimmed from age that I practically needed a flashlight to find
my way around.

 

[Victor Roberts]

Obviously they use some sort of driver circuit to control current to the
lamp via the triac. I would have assumed you knew that - from your own
website.

Are you claiming that your "ballast" has no inductor or no capacitor?
That the only device connected between the lamp and the power line is
a triac?

The problem with a triac is that once it is on it will not turn off
until the current drops to zero. Triacs can be used to dim
incandescent lamps by cutting off the early part of the 50 or 60 Hz
power line cycle. However, the resulting on time, while a fraction of
the a normal half-cycle, is far too long for a fluorescent lamp, which
can run away in far less than 1 msec in less the current is
controlled.

There are circuits where a secondary triac is used to dump reverse
current through the main triac and therefore force it to turn off. I
have never seen these used for a lamp ballast, and I'm not sure they
can switch fast enough to keep the lamp from running away. It would
also require two triacs which is inconsistent with your message.

Are you sure it is a triac? The lamp current can be controlled by
quickly switching a BJT or FET, but that mode creates a lot of EMI.

--
Vic Roberts
http://www.RobertsResearchInc.com
To reply via e-mail:
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[NSM]

Spot relamping is not a good idea in a retail business (or most places
really), discharge lamps suffer lumen depreciation as they age and should be
replaced on a time schedule. Otherwise they get dimmer and dimmer while
still consuming full power and if you spot relamp them you get bright spots
and dim spots and overall it just looks shabby. A better approach which is
more cost effective in the longrun is to run the lamps a specified number of
hours and then replace them all at once ...

Yep. In the factory I used to do them all at once. I also washed all
reflectors with soap and water. Saves dragging the scaffold out over and
over again.

N

 

[NSM]

Are you claiming that your "ballast" has no inductor or no capacitor?
That the only device connected between the lamp and the power line is
a triac?

All I know is that the entire ballast is the size of a pack of cigarettes -
I see no cap or choke of any size.

N

 

[Sean]

Thanks for the info. And yes I did see your post about the aquarium light.
When I head to the "big city" I am going to try and find a starter, or a
ballast that will fit. (Whichever I can find quickest, I usually don't have
a lot of time in town.)
Thanks again,
Sean

 

[Sean]

Actually that's a pretty good idea to replace the dead ones in one area with
good 4' lamps, and rearrange the rest of the 8' to make that area look
decent.
Thanks!

 

[Victor Roberts]

All I know is that the entire ballast is the size of a pack of cigarettes -
I see no cap or choke of any size.

The inductor and capacitor used in 2-lamp T12 shoplight-type L-C
ballasts can easily fit into a package the size of a pack of
cigarettes.

--
Vic Roberts
http://www.RobertsResearchInc.com
To reply via e-mail:
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[JM]

quoting:

The inductor and capacitor used in 2-lamp T12 shoplight-type L-C
ballasts can easily fit into a package the size of a pack of
cigarettes.

Is this happen to be a "lights of America" shoplite BTW? Those things pretty
much have what Vic had described (capacitor and small inductor) in series
with the lamps. There is also a triac or triac-like switching device in
these LOA ballasts that rapidly switches the preheating of the lamp
electodes, and LOA marketed this as "instant start".

 

[NSM]

The inductor and capacitor used in 2-lamp T12 shoplight-type L-C
ballasts can easily fit into a package the size of a pack of
cigarettes.

IIRC, these are a single 40 W 4' lamp.

N

 

[Victor Roberts]

IIRC, these are a single 40 W 4' lamp.

That is right. There should be one series L-C ballast per lamp.

--
Vic Roberts
http://www.RobertsResearchInc.com
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[James Sweet]

quoting:


Is this happen to be a "lights of America" shoplite BTW? Those things pretty
much have what Vic had described (capacitor and small inductor) in series
with the lamps. There is also a triac or triac-like switching device in
these LOA ballasts that rapidly switches the preheating of the lamp
electodes, and LOA marketed this as "instant start".

Sounds like a very cheap HF electronic ballast.

 

[Victor Roberts]

Sounds like a very cheap HF electronic ballast.

The ballast is not electronic - it is just a L and C. The starter is
electronic, but this is inactive once the lamp starts.

--
Vic Roberts
http://www.RobertsResearchInc.com
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[TKM]

The ballast is not electronic - it is just a L and C. The starter is
electronic, but this is inactive once the lamp starts.

--
Vic Roberts
http://www.RobertsResearchInc.com
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Sounds also like a device that should have been built into the lamp itself
since its life is probably closer to the lamp life than to the life of the
usual commercial ballast. Wonder why we've not seen that for linear lamps
especially for residential applications.

Terry McGowan